Merge pull request laixintao#7 from laixintao/dependabot/pip/pillow-6.2.0

Bump pillow from 4.2.1 to 6.2.0

Author: laixintao

requirements.txt

@@ -6,7 +6,7 @@ matplotlib==2.0.2
 networkx==1.11
 numpy==1.13.1
 olefile==0.44
-Pillow==4.2.1
+Pillow==6.2.0
 pyparsing==2.2.0
 python-dateutil==2.6.1
 pytz==2017.2